Topic 5.2 Photosynthesis Flashcards
State the word equation for photosynthesis
carbon dioxide + water —> glucose + oxygen
State the symbol equation for photosynthesis
6CO2+ 6H2O —> C6H12O6 + 6O2
What is meant by autotrophic?
organisms make complex organic compounds from simple compounds in their environment
Define photosynthesis
the process by which living organisms, particularly plants and algae, capture the energy from the sun using chlorophyll and use it to convert carbon dioxide and water into simple sugars
What are heterotrophic organisms?
organisms that obtain complex organic molecules by feeding on other living organisms or their dead remains
What is the envelope of a chloroplast?
the outer and inner membranes along with the intermembrane space
What are grana?
stacks of thylakoid membranes within a chloropast
What is a thylakoid?
a membrane disc found in a grana of a chloroplast
What are lamellae?
extensions of the thylakoid membranes which connect 2 or more grana, acting as a support skeleton in the chloroplast, maintaining a working distance between the grana so that they get maximum light and function as efficiently as possible
What is the stroma?
the matrix which surround the grana and contains all the enzymes needed to complete the process of photosynthesis and produce glucose
What is chlorophyll a?
a blue-green photosynthetic pigment, found in all green plants
What is chlorophyll b?
a yellow-green photosynthetic pigment
What are carotenoids?
photosynthetic pigments made up of orange carotene and yellow xanthophyll
What is phaeophytin?
a grey pigment which is a breakdown product of the other photosynthetic pigments
Define photosystem I
a combination of chlorophyll pigments which absorbs light of 700nm wavelength and involved in cyclic and non-cyclic phosphorylation
Define photosystem II
a combination of chlorophyll pigments which absorbs light of 680nm and only involved in non-cyclic phosphorylation
Where are PSIs found?
intergranal lamellae (join the granum together)
Where are PSIIs found?
on the grana
Define absorption spectrum
the range of different wavelengths of light that a photosynthetic pigment absorbs against the wavelength of light (displayed as a graph)
Define action spectrum
the rate of photosynthesis against the wavelength of light absorbed, displayed as a graph
What are the 2 stages of photosynthesis?
- light-dependent
- light-independent
What does the light-dependent consist of?
photolysis and phosphorylation to generate ATP and split water molecules
What are the 2 types of phosphorylation?
cyclic and non-cyclic
What does the light-independent stage consist of?
the Calvin cycle
Which photosystem is used in cyclic phosphorylation?
photosystem I
Which photosystem is used in non-cyclic phosphorylation?
photosystem I and II
Describe the process of the light-dependent stage
1) electrons become excited and move up an energy level using the energy trapped in the thylakoid membrane
2) The electrons move along the ETC through electron carriers which generates ATP via phosphorylation of ADP
3) In non-cyclic phosphorylation reduced NADP is generated as the electrons and a proton are are transferred to NADP
- both ATP and reduced NADP are used in the light-independent stage
Describe the process of cyclic phosphorylation
1) Photon of light hits chlorophyll molecule in PSI
2) Electron is excited and leaves molecule
3) Electron taken up by an electron acceptor and passed along an ETC to produce ATP
4) Electron returns to chlorophyll molecule in PSI which can be excited again
Describe the process of non-cyclic phosphorylation
1) water molecules split to provide hydrogen ions to reduced NADP
2) photon of light hits chlorophyll and excites them so they are picked up by electron carriers
3) an excited electron from PSII is picked up by electron carriers and passed along ETC to PSI
Describe how carbon fixation takes place in the chloroplasts
- carbon dioxide diffuses into the stroma
- carbon dioxide binds to RuBP using RUBISCO
- resulting in the formation of intermediate 6C compound
State what happens in the Calvin cycle
1) carbon dioxide diffuses into the stroma and bind to RuBP using RUBISCO
2) intermediate 6C compound forms which immediately splits to 2 x GP (3C)
3) GP is reduced by reduced NADP (goes from reduced NADP –> NADP) and ATP from light-dependent stage is used (ATP –> ADP)
4) this forms GALP ( 2 x 3C)
5) GALP loses a C which forms glucose after 6 turns of the Calvin cycle and ATP is used
State the difference between an action spectrum and an absorption spectrum
absorption spectrum shows absorption of light of different wavelengths and action spectrum shows rate of photosynthesis at each wavelength
